The invention relates generally to gas-fired indoor and outdoor furnaces. More particularly, the invention relates to intake manifolds for premix gas-fired furnaces. Natural gas and propane fired furnaces are widely used in commercial and residential environments for heating, including space heating for air conditioning interior spaces. Gas and propane fired furnaces are known to generate and emit oxides of nitrogen (NOx). In general, NOx refers to a group of highly reactive gases that contain nitrogen and oxide in various amounts (e.g., NO, N2O, NO2).